WO2010094783A2 - Feed water degasifier for a solar thermal power station - Google Patents

Abstract

The invention relates to a feed water degasifier comprising a degasifier (8) with a feed water tank (1) connected thereto, said components being integrated into the water/steam cycle of a solar thermal power station that has a heat transfer medium circuit with an associated water/steam cycle. The aim of the invention is to provide a solution, which in terms of the heating and control process provides a less complex way of supplying the degasifier with heating steam in comparison with prior art. To achieve this, at least one additional evaporator (11), which has a line connection (12) on the water side to the feed water region (5) of the feed water tank (1) and a line connection (13) on the steam side to the steam region (6) of the feed water tank (1), is allocated to the feed water tank (1).

Description

 Feedwater degasser of a solar thermal power plant

The invention is directed to a feedwater degasser comprising a degasser with attached feedwater tank: which are integrated in the water / steam cycle of a solar thermal power plant having a heat transfer medium circuit with associated water / steam cycle. Furthermore, the invention is directed to a solar thermal power plant with such a feedwater degasser and to a method for feedwater degassing and / or feed water heating in the water / steam cycle of a solar thermal power plant in a feedwater tank provided with degasser feedwater.

Solar thermal power plants exhibit. frequently a heat transfer medium circuit and a water / steam cycle coupled thereto via a heat exchanger with steam turbine arranged therein for converting thermal energy into mechanical energy and with a connected generator for generating electrical energy. Here, for example, with the help of parabolspiegelförmigen solar elements, which are assembled in individual solar strands to form a solar field, directed solar energy targeted at absorbers, in which the heat transfer medium flows. In such mirror or solar fields, the thermal energy is transferred in this way in a so-called HTF system (heat transfer fluid system) to the heat transfer medium, usually a thermal oil. This thermal oil of the heat transfer medium circuit is then in heat exchangers its thermal energy to the guided in the water / steam cycle water. In the HTF system, the heat transfer medium thermal oil is heated to about 400 ⁰ C, which By heat transfer to the guided in the water / steam cycle water a vapor of about 390 ⁰ C and 100 bar can arise. With the help of the steam, the at least one steam turbine is then operated with a connected generator, which is then condensed and then recycled as water in the water / steam cycle.

Integrated into the heat transfer medium circuit may also be provided a thermal store (TES) to which a part of the heat transfer medium is supplied, which then emits thermal energy to a storage medium in the store. In times of lack of sunshine, the heat storage material or the storage medium of the thermal storage can then release the stored thermal energy back to the heat transfer medium and thus make it usable.

The water in the water / steam cycle must be treated regularly to maintain the functioning of the water / steam cycle. The water / steam cycles of thermal power plants that operate according to the so-called Clausius-Rankine cycle, including the steam / water cycle solar thermal power plants regularly include a designated degasser or feedwater degasser apparatus, in which the so-called main condensate, which the condensed exhaust steam of the steam turbine (s) and demineralized additional water is prepared to boiler feed water and kept or provided in an associated feedwater tank. This treatment of the feedwater comprises the degassing of the main condensate by driving and removing non-condensable gases such as nitrogen, carbon dioxide and oxygen by mechanical trickling of the condensate in the degasser and in particular by there taking place heating of the condensate by 15 to 30 K. Furthermore, the processing includes the control and setting one to be maintained pH, which is achieved by dosing and / or subsequent addition of ammonia. Likewise, the control and adjustment of the (residual) oxygen content in the water is important, which may be done by increasing the BrüdendampfStroms on the upper dished bottom of the degasser. Finally, the treatment of the main condensate to feed water includes the continuous (intermediate) storage of the processed (boiler) feed water in the feedwater tank or feedwater tank to provide continuously and permanently feed water, which can then be fed via so-called high-pressure feedwater pumps to the steam generator.

Furthermore, the known solar thermal power plants often so-called "auxiliary boiler" systems or "auxiliary boiler", which are assigned to the water / steam cycle and / or integrated into these. These auxiliary boiler systems are necessary in order to still be able to produce necessary steam for the process in stand-by mode and when starting up and shutting down the water / steam cycle. These auxiliary boiler systems are typically fossil fired and must, for example, provide surge steam for the shaft seals of the steam turbines, motive steam for the vacuum pumps to evacuate the steam turbine exhaust condensate, and the main condensate and high pressure feedwater preheaters. In addition, heating steam is provided to the degasser with attached feed water tank for the necessary heating and degassing of main condensate at times outside the regular steam generator and / or steam turbine operation by these auxiliary boiler systems. However, these auxiliary boilers ^λλ systems or " ^Hilfskes sei" do not come from the feed water ^tank (s) of the regular main water / steam cycle of the solar thermal power plant Water fed, but have a separate separate water supply.

Such an auxiliary boiler system, especially if it is fossil fueled, immediately reduces the

Environmental friendliness of a solar thermal

Power plant due to the associated CO ₂ exchange.

In particular, such auxiliary boiler systems are technically relatively complex additional equipment, which also make a complex, sensitive and difficult einzugegelnde control necessary.

The invention has for its object to provide a solution that provides a heating and control technically less expensive way to act on the degasser with (heating) steam.

In particular, the possibility should be created, outside the regular "normal ^e steam generator and steam turbine operation for the operating phases of a stand-by operation and / or a startup and / or shutdown operation of the water / steam cycle of a solar thermal power plant steam and / or to provide warm feed water.

In a feedwater degasser and a solar thermal power plant of the type described, this object is achieved in each case that the feedwater tank is associated with at least one auxiliary evaporator with water-side line connection to the feed water of Speisewassertankε and steam-side line connection to the steam region of the feedwater tank.

In a method of the type described is this

Task according to the invention solved in that at least a portion of the feedwater to the feedwater tank associated additional evaporator supplied, evaporated therein and the steam is returned to the steam region of the feedwater tank.

Advantageous embodiments and expedient developments of the subject invention will become apparent from the respective dependent claims.

By the invention, the feedwater tank of the degasser is assigned at least one additional evaporator directly, which is advantageously also in the immediate vicinity of the feedwater tank. This makes it possible to realize a natural circulation between the feedwater tank and the additional evaporator on a short way, which is not difficult to handle heating and control technology. Overall, this creates the opportunity to be able to supply degasser with connected feedwater tank in a complex manner with heating steam. The invention makes it possible to make a degasifier with feed water tank to a multi-functional, thermal Entgaser-, preheating and auxiliary steam generator. Such a system can be used for a rapid, yet gentle start-up and shutdown of a solar thermal power plant and makes an otherwise usually provided, much larger sized auxiliary boiler system superfluous. Here, the term "additional evaporator" has been chosen because the water / steam cycle of the solar thermal power plant of course has a steam generator, the evaporator, superheater, reheater, etc., but which are located further away and in addition to the auxiliary evaporator.

Such a direct assignment of an additional evaporator is of particular advantage when the at least one additional evaporator is replaced by the heat transfer medium of the Heat transfer medium circuit is heated and / or heated, as the invention provides in an embodiment of the feedwater degasser. As a result, for example, a thermal oil-heated Natururαlauf evaporator that makes no separate, own fossil firing more necessary and provides the water / steam cycle for keeping warm and for the startup and shutdown of the solar thermal power plant degassed and preheated feed water available ,

Advantageously, the at least one additional evaporator is heated by means of a partial flow diverted from the heat transfer medium circuit.

The heat transfer medium is in particular a liquid, commonly used thermal oil. The invention is therefore characterized in another embodiment by the fact that the heat transfer medium is a Therrαoöl and / or the additional evaporator is a natural circulation evaporator.

In order to integrate the feedwater degasser according to the invention and the feedwater tank without changes to conventional water / Dampfkreislaufsystemen in this and connected to a water / steam cycle, according to another embodiment of the invention provides that the feedwater tank via a feedwater and the feedwater via a main condensate in the water / Steam cycle is involved.

A particularly expedient embodiment of an evaporator can be formed in that the additional evaporator is designed as a heat exchanger. This offers the possibility to guide the heat transfer medium in Gegenstronα to circulating in the natural circulation and boiling feed water through a designed as a heat exchanger auxiliary evaporator, wherein then the water boiling in the additional evaporator is fed into the heat exchanger tubes and the liquid heat transfer medium in the form of the thermal oil runs along the outside of the heat exchanger tubes. The invention therefore further provides that the additional evaporator is a heat exchanger.

Since the inventive design of the feedwater degasser with attached feedwater tank; by allocating an additional evaporator makes a usual auxiliary boiler system superfluous, the solar thermal power plant according to the invention is characterized in an embodiment in that it has no auxiliary boiler associated with the heat transfer medium circuit and / or the water / steam cycle, in particular not solar-heated.

Furthermore, it is advantageous if the solar thermal power plant has a feedwater tank according to one of claims 2 to 6, which the invention also provides. The solar thermal power plant then has the same advantages as mentioned above in connection with the feedwater degasser.

In the context of a solar thermal power plant, which is equipped with a heat transfer medium circuit incorporating the respective solar field, it is expedient to heat the auxiliary evaporator with this heat transfer medium, which may be in particular thermal oil. The inventive method therefore provides in an embodiment that the additional evaporator is heated by the heat transfer medium of the heat transfer medium circulation.

It is then of particular advantage if the

Feed water between the feedwater tank and additional evaporator is moved by means of natural circulation, what the invention also provides. This makes it possible to provide a degasser for different Betriebsrnodi the solar power plant available, arranged with its associated and especially in the vicinity of the feedwater tank and preferably thermo-heated Naturumlauf Zusatzverdainpfers permanently and highly flexible, quickly and safely regulated preheated and degassed feed water and Can provide auxiliary steam in a large mass flow bandwidth for the water / steam cycle of the solar thermal power plant.

With the branching of a HTF partial flow, it is possible to provide a heating of the additional evaporator without great regulatory technical and / or constructive and / or line effort.

Urα the additional evaporator and thus standing in line and operative connection degasser with feedwater tank as a multifunctional thermal degassing, preheating and auxiliary steam generator for the water / steam cycle of solar thermal power plant to train, it is also advantageous if the additional evaporator 0, 5% to 45% of the steam / water cycle at steam turbine full load total provided feedwater flow are supplied.

In this case, according to a further development of the invention, there is the possibility that the feed water of the feed water tank is kept at a temperature in the region of its boiling point in the stand-by operating mode of the power plant by circulation through the auxiliary evaporator. As a result, at any time sufficiently hot feed water for a rapid warm start of the / the steam generator (s) and the steam turbine (s) available. Since the auxiliary evaporator in the stand-by operating mode of

Power plant for this mode of operation

What ser / steam cycle can provide enough auxiliary steam available, it is then still advantageous if no supply of external auxiliary steam takes place in the stand-by mode, whereby the invention is also characterized.

Here, the evaporator is then in the stand-by mode with minimal heat transfer medium throughput z and operate at minimum power.

With the inventive combination of

The feedwater degasser, feedwater tank and auxiliary evaporator can be used in addition to keeping the feed water in stand-by mode of operation of the solar thermal power station warm, but also to support the warm start or warm start-up of the power plant. The additional evaporator can namely provide a water vapor mass flow, which goes well beyond the water vapor mass flow required for a pure keeping warm, the feedwater. Until it reaches its full thermal load, the additional evaporator can therefore be used for starting or starting up the power plant. The inventive method therefore provides finally in an embodiment that in the warm start / warm start mode of the power plant, the thermal power of the additional evaporator he stepless ramped up to its full thermal load and thereby the vapor pressure by means of a vapor pressure setpoint control is controlled.

After carrying out the starting process of the power plant then the additional evaporator is preferably after reaching his

Full load range back again, in which case the thermal energy required for the degasser as otherwise in

Water / steam cycle of solar thermal power plants übl I, by means of the degasser supplied tapping steam is provided. The invention is therefore characterized Finally, characterized in that when a predetermined (fresh) steam pressure, in particular in the main steam line, and / or upon reaching a certain partial load range of the steam turbine of the power plant to the degasser tapped steam supplied from the water / steam cycle and the auxiliary evaporator in a stand-by Warming mode is switched and operated in this.

It goes without saying that the features mentioned above and those yet to be explained below can be used not only in the respectively specified combination but also in other combinations. The scope of the invention is defined only by the claims.

The invention is explained below with reference to an embodiment with reference to an accompanying drawing. This shows in the single figure in scherαatischer representation of the arrangement of a feedwater according to the invention degassing associated with feedwater tank and this associated additional evaporator.

The single FIGURE shows a horizontally disposed cylindrical feedwater tank or feedwater tank 1, in which the bottom side feedwater 2 and in the area formed above saturated steam 3 The filled up to the liquid bath 4 with feed water 2 area of the feedwater tank 1 is hereinafter referred to as Ξspeisewasserbereich 5 and the above formed area referred to as steam area 6 of the feedwater tank 1. In the feed water area 5 degassed feed water for the water / steam cycle of the not shown, connected solar thermal power plant is provided and kept. To the water / steam cycle of the feedwater tank 1 is connected via a feedwater line 7 through which the water / steam cycle in Direction of the arrow shown in the tube 7 degassed feed water 2 is supplied.

Above the steam region 6, a vertical cylindrical degasser 8, in the present exemplary embodiment a Rieseltassen degasser, is arranged on the feedwater tank 1. It is connected via a unabsperrbar trained flange 9 with the steam region 6 of the feedwater tank 1 in combination. In the upper region of the degasser 8, the main condensate line 10, via which the degassing / feedwater tank combination according to the invention is integrated downstream of the steam turbines into the water / steam cycle of the power station, opens on the steam side.

Furthermore, the feedwater tank 1, an additional evaporator 11, in particular local, assigned and also arranged laterally close to the feedwater tank 1. The additional evaporator 11 has a water-side line connection 12 to the feedwater region 5 of the feedwater tank 1 and a steam-side line connection 13 to the steam region 6 of the feedwater tank 1. By heating the formed in the form of a heat exchanger auxiliary evaporator 11 can be formed in the line connections 12, 13 from the feedwater tank 1 to the additional evaporator 11 and the auxiliary evaporator 11 back to the feedwater tank 1 based on the so-called thermosiphon principle natural circulation of the feedwater 2. The heating of the additional evaporator 11 takes place by means of the circulating in the heat transfer medium circuit of the associated solar thermal power plant heat transfer medium, which is a thermal oil in the embodiment. The heat transfer medium is the additional evaporator 1 (s) supplied to a higher temperature level via a supply line 14 and at a lower temperature level via the discharge line 15 back out of the additional evaporator 11 out and fed to the heat transfer medium circuit. The executed in the embodiment as a thermal oil-heated natural circulation additional evaporator evaporator 11 includes a straight tube heat exchanger in which the fed through the supply line 14 warm thermal oil is led outside the heat exchanger tubes to the discharge line 15 and countercurrently to the fed through the water-side line connection 12 Feed water 2 boiling and optionally evaporating the steam-side line connection 13 is supplied. The auxiliary evaporator 11 is mounted laterally on or at least in the vicinity of the feedwater tank 1, so that the line connections 12, 13 can be made relatively short.

Furthermore, a vertical expansion bottle 16 is arranged on the feedwater tank 1, which at one end also has a water-side line connection to the feedwater region 5 of the feedwater tank 1 and at the other end a steam-side line connection to the steam region 6 of the feedwater tank 1. In the flash bottle 16 opens a line 17 through which originating from the high-pressure feed water preheaters of the water / steam cycle heating steam condensate in the flasher 16 is introduced and from there smoothly in the feedwater tank 1 traceable.

On its side facing away from the feedwater tank 1, the degasser 8 is further connected by line to a main condensate-cooled brine steam condenser 18. The Brüdendampfkondensator 18 is designed as a recumbent straight pipe heat exchanger, which flows via a supplied from the main condensate line 10 via a branched line 10a cooling main condensate in the heat exchanger tubes and is returned via a branch line 10b in the main condensate line 10. Outside the heat exchanger tubes of the Brüdendampfkondensators 18 of the resulting degassers 8 and the non-condensable gases, such as CO ₂ , O ₂ or N ₂ containing Brüdendampf passed. As a result, the water-containing parts of the Brüdendampfes condense, which are then recycled as condensate via a line 19 back into the steam region 6 of the feedwater tank 1. The remaining, non-condensing gas components, in particular the CO2, O ₂ and N ₂ to be degassed, are discharged via a line 20 as exhaust gas 21.

With the help of the additional evaporator 11, it is possible to heat the feed water 2, which can be regulated and controlled, so that with the help of the additional evaporator 11 in a particular operating mode of the solar thermal power plant desired targeted evaporation of feed water can be done. As a result of this additional unit, the degasifier / feedwater tank arrangement, which is conventionally conventionally designed in principle, is designed as a multifunctional, thermal degassing, preheating and auxiliary steam generator installation. This can be used for a more rapid and yet gentle start-up and shutdown of the solar thermal power plant, d. H. its regular water / steam cycle, are used. A separate, and usually fossil-fired auxiliary boiler system, which is otherwise necessary for this purpose in conventional solar thermal power plants, is therefore no longer necessary.

The addition of the degasser 8 and the feedwater tank 1 and the additional evaporator 11 in the form of thermal oil-heated

Natural circulation evaporator comprehensive combination provides the

Water / steam cycle of the connected and associated solar thermal power plant via the feed water line 7 for keeping warm and for the startup and shutdown of the solar thermal power plant degassed and preheated Feed water in the feedwater tank: 1 available. Here, depending on the operating state of the solar thermal power plant, the feedwater tank 1 preheated feedwater 2 removed in an amount and recycled after flowing through the additional evaporator 11 back into this, which corresponds to 0.5% to 45% of the throughput of feedwater mass flow of the feedwater tank 1 in the Keeping warm or starting subsequent ordinary operating mode previous or preceding the departure, especially in steam turbine full load operation is taken, in which the usual, explained below, preheating of the feedwater 2 by means of line 10 supplied main condensate.

With the invention, a combination of degasser 8, feedwater tank 1 and additional evaporator 11 is provided, which by means of the thermal oil-heated natural circulation evaporator 11 permanent and highly flexible, quickly and safely adjustable auxiliary steam in a (large) mass flow bandwidth of 0.22 - 5kg steam / s for the water / steam cycle.

With the feedwater degasser 8 according to the invention, delivery of the smallest auxiliary vapor mass flows in the range of 0.22-0.25 kg steam / s in the standby operating mode of the solar thermal power plant is possible first of all. In this stand-by mode of operation in which the water / steam cycle is kept ready for the next warm start, micro-auxiliary mass flows of 0.22 kg / s - 0.25 kg / s flow stably and quickly by means of a set steam pressure setpoint controlled and controlled by the saturated steam region 6 of the feedwater tank 1 via a line 22 as auxiliary steam or foreign steam in the auxiliary steam collector, not shown, of the water / steam cycle of the connected solar thermal power plant and from there into the sealing steam system of associated or associated steam turbine and in the motive steam system of the vacuum pump evacuation system of the water / steam cycle. In this operating state of the auxiliary steam collector is quasi "backwards" supplied with auxiliary steam, since the feedwater tank 1 with associated feedwater degasser 8 generates and delivers auxiliary steam in this operating condition, but no steam, as it is supplied for example via the bleed steam line 23 in the ordinary mode of operation of the power plant needed and consumed.

At the same time and in parallel to the delivery of auxiliary steam, the feed water 2 is kept warm in the feedwater tank 1 without external external steam supply from the outside alone with the help of circulating through the auxiliary evaporator 11 feed water circulation in this stand-by operating mode of the power plant. Since no steam and thus water is supplied from the outside, there is no increase in the liquid bath level 4, with the result that eventually feed water would have to be drained from the feedwater tank 1, as is necessary in previously conventionally operated Essensgewasserentgasern according to the prior art. The feedwater degasser 8 according to the invention with feedwater tank 1 contains feedwater 2 which is at a temperature in the range of its boiling point and which can be made available to the water / steam cycle via the feedwater line 7 at any time, for example if startup of the steam generator and steam turbine is to take place.

The thermal oil-heated natural circulation evaporator 11 is operated in this stand-by operating mode of the power plant with a minimum thermal oil flow rate of about 22 kg / s at a minimum power of about 0.44 MW, the required thermal oil from the return of the already required Thermal oil circulation in the heat transfer medium circulation of the Power plant branched off and returned there. This diversion of heat transfer medium for heating the additional evaporator 1 from the return section of the heat transfer medium circuit makes it possible to supply the auxiliary evaporator 11 heat transfer medium, without that additional auxiliary equipment is required only for this purpose, which would then be kept inactive in the ordinary mode of operation of the power plant.

The inventive combination of degasser 8, feedwater tank 1 and additional evaporator 11 also provides support during warm start / warm start of steam generator and steam turbine when the power plant is in a warm start / warm start mode. In this mode, the thermal performance of the thermal oil-heated natural circulation evaporator 11 is continuously increased from the low load (0.44 MW} regulated in standby mode to its full thermal load (10 MW) while being stable by means of a vapor pressure set point control When the full thermal load in the additional evaporator 11 of 10 MW is reached, approximately twice the thermal power is transferred to the main condensate within the feedwater degasser system or within the degasser 8 for the rapid steam generator startup, which is operated in regular, full-load, stationary operation The full load in the auxiliary evaporator 11 of 10 MW in the final stage of the boiler and steam turbine start-up means reaching 200% of the nominal heat transfer line in the feedwater degassing system or in the degasser 8, which is achieved at full steam turbine load.

This high, twice the thermal power consumption of

Additional evaporator 11 also results from the fact that in this operating state by the main condensate 10th flowing main condensate is still cold and thus not only by the usual order of 15 to 30 K in the degasser 8 must be heated to the necessary temperature for the thermal degassing, but in the order of 110 to 120 K must be heated to those for the Feedwater preheating and evaporation to obtain necessary temperature.

In Rieseltassen degasser 8 is about 2 times the nominal heat transfer performance implemented.

In di-eser warm start / warm start-up phase, the steam flow rate in the steam generator and in the steam turbine is increased according to the respective predetermined temperature gradient and the feedwater tank 1 is supplied according to the steam generator and the steam turbine to be supplied by feed water via feed water for the seventh preheated feedwater 2 removed. As a result, the feed water level, ie the feed water level 4, drops in the feed water tank 1 and falls below a predetermined water level setpoint. In this way, a control valve is opened by means of a water level regulator, which causes the main condensate to flow via the main condensate line 10 into the degasser 8. The main condensate which has entered the degasser 8 then trickles uniformly from top to bottom over the trickle cups of the degasifier 8, while at the same time saturated steam flows from the steam region 6 of the feedwater tank 1 countercurrently from bottom to top through the degasser. In the course of the countercurrent, the saturated steam flowing through the degasser condenses successively in direct contact with the main condensate and releases its heat of condensation or evaporation enthalpy to the main condensate. This increases the temperature of the main condensate and the non-condensable gases contained therein, in particular CO ₂ , O ₂ and N ₂ , dissolve thereby inevitably from the getting hotter main condensate and escape with the so-called Brüdendampf from the degasifier 8 and are supplied to the line Brüdendampf-condenser 18, from which they then escape via line 20 as exhaust 21 from the water / steam cycle.

In the brine vapor condenser 18, the broth steam is cooled and condensed by means of the main condensate fed into heat exchanger tubes and supplied via a line 10a. The Brüdendampf condenses almost completely and is recycled via the line 19 water in the feedwater tank 1. The non-condensable gases (CO ₂ , O ₂ , N ₂ ) are discharged with a minimum remainder of the Brüdendampfes via line 20 as exhaust 21 into the ambient air or atmosphere.

In the process described above, saturated steam from the steam region 6 of the feed water tank 1 flows into the degasser 8 and condenses there on the main condensate flowing in the opposite direction. As a result, the vapor pressure in the vapor region 6 of the feed water tank 1 drops, whereupon a vapor pressure regulator opens a control valve in the feed line 14, so that the. Evaporator 11 hot, located at its higher temperature level heat transfer medium, in the present case thermal oil, fed or supplied in a larger amount. This results in the additional evaporator 11 between the side of the supply line 14 and the side of the discharge line 15, a larger temperature gradient, whereby the connected via the lines 12 and 13 natural circulation for the feed water immediately without delay and without any fluid and / or thermodynamic barriers, such as unwanted steam implosions, accelerated. As a result, the fed through the additional evaporator 11 feedwater mass flow is accelerated, more feed water per Time unit evaporates, and the vapor pressure in the vapor region 6 increases again. By means of the additional evaporator 11 as much feed water is evaporated, as is necessary for heating, degassing and reboiling of the main condensate and to maintain the desired and set vapor pressure in the vapor pressure range 6.

Finally, the combination of feedwater degasser 8, feedwater tank 1 and auxiliary evaporator 11 is then operated again in a stand-by mode when the steam generator and the steam turbine have reached their normal operating condition and / or while the steam generator and the steam turbine or the steam generator set in the operating state of the ramp-up pressure mode.

This stand-by mode of the degasser 8 according to the invention is set as soon as a certain, desired live steam pressure is established in the steam generator and / or in the main steam line and the steam turbine has reached a desired, certain partial load range, this limit preferably being reached when the connected to the steam turbine generator has reached 20% of its generator power. In this case, the stand-by mode of the degasser 8 is then initiated by the heating power of the thermal oil-heated natural circulation evaporator 11 is withdrawn by throttling the inflowing thermal oil as the heat transfer medium. At the same time then flows through the bleed steam line 23 supplied heating steam through the degasser 8, where it causes the corresponding degassing of the opposing Ilauptkondensats. In this operating state of the solar thermal power plant, the main condensate now has an elevated temperature compared to the start-up mode, so there is no longer any "cold" main condensate since this can be preheated by heat exchangers charged with heating steam Mode, the auxiliary evaporator 11 is connected to the connected supply 14 and programmed so that it then starts and again provides more thermal power for heating feed water available, if there is a sudden and undesirable pressure drop in the degasser 8 and / or the feedwater tank. 1 comes, which is not immediately compensated by increasingly supplied through the line 23 tap or heating steam.

Incidentally, the auxiliary evaporator 11 is operated in this evaporator stand-by mode of operation again only with a minimum thermal oil flow rate of <8 kg / s, so that a low feed water circulation takes place. Due to ZufHeßens of heat transfer medium, the supply line 14, and by the circulation of the feedwater caused thereby, the auxiliary evaporator 11 is maintained with water-side line connection 12 and steam-side line connection 13 each warm and at operating temperature. In particular, this measure makes it possible that by means of the additional evaporator 11 saturated steam can be generated in the short term, if in the degasifier 8 and / or in the feedwater tank 1, the vapor pressure drops.

In this case, it is provided that the desired value of a pressure-maintaining regulator slides with the pressure actual value in the feedwater tank 1 and "freezes" this actual value if a certain pressure drop gradient is exceeded the availability of the power plant process is guaranteed and / or increased overall.

Altogether, the system components solar field, HTF (heat transfer fluid) system and thermal storage (TES) provided within the scope of a solar thermal power plant are optimally utilized and integrated into the feedwater degassing, so that after one State of the art usually required conventional, in particular fossil fuel fired, additional auxiliary boiler system for generating auxiliary steam can be dispensed with.

The thermal energy generated in the solar field of the solar thermal power plant can be made available to the auxiliary evaporator 11 and / or the feed water 2 in four different ways:

1. In normal operation in ^" sunshine radiation, the thermal energy is supplied via the heated in the solar field heat transfer medium {Heat T_ransfer jTluid) directly via the supply line 14.

2. In non-sunshine periods, thermal energy can be transferred to the heat transfer medium (HTF) from a thermal store (TES). For example, it may be in the thermal storage to a molten salt heat storage, which then in the discharge mode, the stored thermal energy to the heat transfer medium, in the exemplary embodiment thermal oil, which then feeds the thermal energy via the supply line 14 to the additional evaporator 11.

3. Stored thermal energy can be released as residual heat through the heat transfer medium to the auxiliary evaporator 11. After switching off or eliminating all the above-mentioned heat sources, the HTF mass (about 2000 t} from the heat transfer circuit heat to the auxiliary evaporator 11 release until it has cooled from about 300 ⁰ C to about 190 ⁰ C.

4. Thermal energy from the combustion of natural gas in the so-called heat transfer fluid heater can be provided via the heat transfer medium. at If certain HTF temperatures are not reached, the HTF is brought to or maintained at temperature, depending on the mode of operation with natural gas combustion.

The inventive combination of the degasser 8 with the feed tank 1 and the associated additional evaporator 11 leads to a number of other advantages. Thus, with this system, a simple, heating and control technically unproblematic cold start of the evaporator and the feedwater degasser due to the based on the principle of the thermo-siphon principle natural circulation of the additional evaporator or heat exchanger possible. There are no separate installations in the feedwater tank and no separate steam lines, complicated control systems, etc., necessary. For the operation of the additional evaporator 11, it is sufficient to divert a supply line 14 from the heat transfer medium circuit and return a discharge line 15 thereto. Additional pumps to guide the heat transfer medium through the lines 14 and 15 and the auxiliary evaporator 11 are not necessary. The pumps circulating the heat transfer medium in the heat transfer medium circuit are sufficient to also transport the heat transfer medium through the lines 14, 15.

Claims

Patentansorüche 1. Feedwater degasser comprising a degasser {8) with attached feedwater tank {1), which in the water / steam cycle of a Heat transfer medium circuit with associated water / steam cycle solar thermal power plant are involved, characterized in that the feedwater tank (1) at least one auxiliary evaporator (11) with water-side line connection (12) to the feed water area (5) of the feedwater tank (1) and with vapor-side line connection (13) associated with the steam area {6} of the feedwater tank (1). 2. feedwater degasser according to claim 1, characterized in that the at least one additional evaporator (11) by means of the heat transfer medium of the heat transfer medium circuit is heated and / or heated. 3. feedwater degasser according to claim 1 or 2, characterized in that the at least one Zusatzverdarαpfer (11) is heated and / or heated by means of a diverted from the heat transfer medium circuit partial flow. 4. Feedwater degasser according to one of the preceding claims, characterized in that the heat transfer medium is a thermal oil and / or the auxiliary evaporator (11) is a natural circulation evaporator. 5. feedwater degasser according to one of the preceding claims, characterized in that the feedwater tank (1) via a feedwater line (7) and the feedwater degasser (8) via a main condensate line (10) is integrated into the water / steam cycle. 6. feedwater degasser according to any one of the preceding claims, characterized in that the additional evaporator (11) is a heat exchanger. 7. Solar thermal power plant with a degasser (8) with connected feedwater tank (1} comprehensive feedwater degasser, which in the water / steam cycle of the one At least one auxiliary evaporator (11) with water-side line connection (12) to the feed water area (5) of the feed water tank (1) and with steam-side line connection (13) for Steam region (6) of the feedwater tank (1} is assigned. 8. Solar thermal power plant according to claim 7, characterized in that it does not have the heat transfer medium circuit and / or the water / steam cycle associated, in particular not solar heated, auxiliary boiler. 9. Solar thermal power plant according to claim 7 or 8, characterized in that it comprises a feedwater degasser (8) according to one of claims 2 to 6. 10. A method for feedwater degassing and / or feed water heating in the water / steam cycle of a solar thermal power plant in a feedwater tank (1) with degasser (8) provided feedwater (2), characterized in that at least a part of Feedwater (2) one the feedwater tank (1) with Degasser (8) associated additional evaporator (11) fed, evaporated therein and the steam in the steam region (6) of the feedwater tank (1) is recycled. 11. The method according to claim 10, characterized in that the additional evaporator (11) from the heat transfer medium of the heat transfer medium circulation, in particular a diverted partial flow, is heated. 12. The method according to claim 10 or 11, characterized in that the feed water (2) between the Ξpeisewassertank (1) and the auxiliary evaporator (11) is moved by means of natural circulation. 13. The method according to any one of claims 10 to 12, characterized in that the additional evaporator (11} 0.5 to 45% of the steam / water cycle at steam turbine full load total provided feedwater mass flow are supplied. 14. The method according to any one of claims 10 to 13, characterized in that the feed water (2) of the Feedwater tanks (1) in the stand-by mode of operation of the power plant by circulation through the auxiliary evaporator (11) is maintained at a temperature in the range of its boiling point. 15. The method according to any one of claims 10 to 14, characterized in that in the stand-by mode of operation of the power plant no supply of external auxiliary steam in the degasser {8). 16. The method according to any one of claims 10 to 15, characterized in that in the warm start / warm start mode of the power plant, the thermal power of the auxiliary evaporator {11) ramped up to its full thermal load and controlled the vapor pressure by means of a vapor pressure setpoint control becomes. 17. The method according to any one of the preceding claims, characterized in that upon reaching a predetermined (fresh) steam pressure, in particular in the main steam line, and / or upon reaching a certain partial load range of the steam turbine of the power plant, the degasser (8} tapping steam from the water / Steam cycle supplied and the auxiliary evaporator (11) is switched to a stand-by-warming mode and operated in this.